Railroad tank cars are well known and useful for carrying liquid commodities. A typical general purpose, non-pressurized railroad tank car is indicated in general at 22 in FIGS. 1 and 2. The tank car features a tank body 24 mounted on a pair of wheel trucks 26a and 26b. 
As illustrated in FIGS. 1 and 2, a manway cover 28 is positioned on top of a nozzle 30 which is mounted on the tank body 24. As is known in the art, the manway cover pivots open and may be accessed by a ladder 32. The manway cover permits access to the interior of the tank body 24. Manway covers are typically designed to fit a 20″ inner diameter manway nozzle. Nozzles having other inner diameters, however, have been made. These include nozzles having 24″, 21″, 18½″ and 18″ inner diameters.
A prior art manway cover and nozzle is illustrated in FIGS. 3 and 4. The manway cover is secured in the closed configuration on the nozzle by fasteners (eyebolts) that are spaced about the circumference of the manway cover. The typical quantity of eyebolts is either 6 (as illustrated in FIGS. 3 and 4) or 8, however, the industry does have, on rare occasions, 10 bolt arrangements. The eyebolt nuts are individually loosened or tightened in a star pattern with a wrench or similar tool when the manway cover is opened or closed, respectively.
The manway cover features a hinge that permits it to be pivoted from the closed configuration, illustrated in FIGS. 3 and 4, to an open configuration via the handle so that access to the manway is permitted. The manway cover of FIGS. 3 and 4 is equipped with a torsion spring arrangement (Labeled “UTC E-Z Lift” in FIG. 4) at the hinge that aids in the lifting of the cover while opening. The two eyebolts nearest the handle act as safety bolts in that they secure the cover in place while allowing pressure to be relieved in a safe manner. The cover must be slightly opened before the safety eyebolts may be disengaged so that the cover may be pivoted open completely.
All manway cover designs must be approved by the Association of American Railroad Tank Car Committee (AAR/TCC).
Manways are used for several purposes including dome loading or unloading, entry into the tank car, venting (by opening the manway cover), access to view gauging level and commodity sampling. The primary use of the manway at the loading rack is to open for dome loading, while the primary use at the unloading rack is for venting.
Issues with current manway nozzle and cover designs include out of round nozzles, out of flat nozzle and gasket grooves, loose hinge movements that cause interference with fit ups between the manway nozzle and cover, inconsistent sealing, difficulty of assembly and disassembly and loose eyebolts.
Prior art manway covers have been identified as a location where non-accidental leaks consistently occur. Indeed, as illustrated by the graphs of FIGS. 5 and 6, manway covers are the largest contributor to non-accidental releases (NARs) for non-pressurized cars in transit.
In view of the above, it is desirable for manway nozzle and cover designs to feature a round nozzle and a seating surface that is flat. In addition, one input from the operator to secure the manway fasteners is desirable over the 6 to 10 individual inputs required by prior art designs. A repeatable placement of the cover and clamping force on the gasket is also preferable.